Antenna device and electronic equipment

ABSTRACT

An antenna device includes a radiating element, a coupling circuit, and a non-radiating resonant circuit. The coupling circuit includes first and second coupling elements, the first coupling element being connected between a feeder circuit and the radiating element, the second coupling element being coupled to the first coupling element. An end of the second coupling element is grounded, and another end of the second coupling element is connected to the non-radiating resonant circuit. A frequency characteristic of a return loss of the radiating element when seen from the feeder circuit is adjusted by a resonant frequency characteristic of the non-radiating resonant circuit.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese PatentApplication No. 2016-231024 filed on Nov. 29, 2016, Japanese PatentApplication No. 2016-255729 filed on Dec. 28, 2016, Japanese PatentApplication No. 2017-082043 filed on Apr. 18, 2017, Japanese PatentApplication No. 2017-104650 filed on May 26, 2017, and Japanese PatentApplication No. 2017-158218 filed on Aug. 18, 2017, and is aContinuation Application of PCT Application No. PCT/JP2017/042706 filedon Nov. 29, 2017. The entire contents of each of these applications arehereby incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an antenna device that complies with awide frequency band and electronic equipment including the antennadevice.

2. Description of the Related Art

In order to broaden a frequency band or to comply with a plurality offrequency bands, an antenna device including two radiating elements thatare directly or indirectly coupled to each other is used. In addition,International Publication No. 2012/53690 illustrates an antenna deviceincluding two radiating elements and a coupling degree adjustmentcircuit that controls power feeding to the two radiating elements.

In the antenna device illustrated in International Publication No.2012/153690, the first radiating element and the second radiatingelement are coupled to each other via the transformer, and a feedercircuit and the antenna device are matched by a setting of the coupling.Since the first radiating element and the second radiating element donot have to be arranged in parallel to each other in the antenna deviceillustrated in International Publication No. 2012/153690, design of thepatterns for the first radiating element and the second radiatingelement has a high degree of freedom. In addition, even if the firstradiating element and the second radiating element are disposed closerto each other, a predetermined coupling degree is able to be set. Thismakes it easy to match the feeder circuit and a multi-resonance antenna.

However, in a frequency band in which one of the radiating elementslargely contributes to radiation, when radiation from the other of theradiating elements influences radiation of the one of the radiatingelements, a desired radiation characteristic might not be obtained,which degrades a radiation characteristic of an antenna.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide antenna devicesthat each avoid an issue of interference regarding radiation of tworadiating elements so as to broaden the band and electronic equipmentincluding the antenna devices.

An antenna device according to a preferred embodiment of the presentinvention includes a radiating element; a coupling circuit including afirst coupling element and a second coupling element, the first couplingelement being connected between the radiating element and a feedercircuit, the second coupling element being coupled to the first couplingelement; and a non-radiating resonant circuit connected to the secondcoupling element, in which a frequency characteristic of a return lossof the radiating element is adjusted by a resonant frequencycharacteristic of the non-radiating resonant circuit.

With the above-described configuration, the radiating element and thenon-radiating resonant circuit do not interfere with each otherregarding radiation, in view of the radiating element being connected tothe first coupling element of the coupling circuit and the non-radiatingresonant circuit being connected to the second coupling element of thecoupling circuit, and a radiation characteristic of the radiatingelement is not adversely affected. In addition, the frequencycharacteristic of a return loss of the radiating element seen from thefeeder circuit is adjusted by a resonance characteristic of thenon-radiating resonant circuit, and a pole is generated in a desiredfrequency band to broaden the band of the frequency characteristic ofthe antenna.

It is preferable that a direction of a magnetic field generated whencurrent flows in the first coupling element in a direction from aterminal connected to the feeder circuit to a terminal connected to theradiating element is opposite to a direction of a magnetic fieldgenerated when current flows in the second coupling element in adirection from a terminal connected to the non-radiating resonantcircuit to a terminal connected to a ground. Thus, a mutual inductancedue to the coupling between the first coupling element and the secondcoupling element decreases inductances of the first coupling element andthe second coupling element, so as to have little influence on a circuitcharacteristic and the radiation characteristic of the radiatingelement.

It is preferable that the first coupling element and the second couplingelement are multi-layered coil conductor patterns, and that the couplingcircuit defines a transformer in which the first coupling element andthe second coupling element are electromagnetically coupled to eachother. Thus, a coupling circuit with a high coupling coefficient betweenthe first coupling element and the second coupling element is provided,and the resonance characteristic of the non-radiating resonant circuitwhen seeing from the feeder circuit is likely to be shown.

It is preferable that about half or more of the non-radiating resonantcircuit is included within a formation region of the radiating elementin a plan view of the radiating element. Thus, the non-radiatingresonant circuit is shielded by the radiating element. This increases anon-radiating property of the non-radiating resonant circuit seen from adistance.

It is preferable that the radiating element is defined by a conductivemember that includes three sides in a plan view, and that thenon-radiating resonant circuit is surrounded by the three sides in aplan view. Thus, the non-radiating resonant circuit is shielded by theradiating element. This increases the non-radiating property of thenon-radiating resonant circuit seen from a distance.

It is preferable that the non-radiating resonant circuit is defined by alinear conductor pattern that includes a returning portion along thelinear conductor pattern. Thus, sharpness of the resonance of thenon-radiating resonant circuit is degraded, and the non-radiatingresonant circuit is able to attenuate a reflection coefficient in arelatively wide band including the band in which the pole generated inthe frequency characteristic of the antenna and its periphery. Inaddition, the non-radiating resonant circuit is able to be provided in asmall area.

It is preferable that the conductor pattern includes a first linearconductor pattern portion that extends from the coupling circuit and asecond conductor pattern portion that returns, at the returning portion,to be away from the radiating element. This reduces or preventsunnecessary coupling between the non-radiating resonant circuit and theradiating element.

It is preferable to further include a phase shifter that is connectedbetween the feeder circuit and the first coupling element and that has afrequency dependency. This makes it possible to provide an antennadevice that performs impedance matching in a wide band.

It is preferable that a second terminal of the second coupling elementis connected to the ground, the second terminal being opposite to afirst terminal to which the non-radiating resonant circuit is connected,and that a length of a line between the first coupling element and thefeeder circuit and a length of a line between the second terminal of thesecond coupling element and the ground are each less than about ⅛wavelength of a resonant frequency.

Since the coupling circuit mainly uses magnetic field coupling, thestrength of coupling is increased when the coupling circuit is includedat a portion at which a strong current flows. The strong coupling isable to improve the influence of resonance obtained by adding thecoupling circuit and the parasitic element, and since a resonantbandwidth is broadened, a frequency band in which communication ispossible is broadened. In addition, a signal intensity is increased, anda communication characteristic is improved.

The antenna device may include an inductor that is connected between thesecond coupling element and the non-radiating resonant circuit. Thus,since the inductor is included at a portion at which current is low,while a change in the coupling is reduced or prevented (change inimpedance matching is reduced or prevented), the resonant frequency onthe non-radiating resonant circuit side is able to be decreased, and adesired communication band is able to be obtained. Alternatively, whilethe resonant frequency is maintained, the length of the non-radiatingresonant circuit is able to be reduced, and thus the area used is ableto be reduced.

The antenna device may include an inductor that is connected between thefirst terminal of the second coupling element and the ground. Thus,reactance generated by a parasitic capacitance between the ground andthe coupling circuit by insertion of the coupling circuit is able to besuppressed, and a change from a matching state in which the couplingcircuit is not mounted is able to be reduced or prevented. In addition,the resonant frequency of the non-radiating resonant circuit is able tobe decreased, and a desired communication band or communicationcharacteristic is able to be obtained. Alternatively, while the resonantfrequency is maintained, the length of the antenna is able to bereduced, and thus the area used is able to be reduced.

The antenna device may further include a capacitor that is connectedbetween the second coupling element and the non-radiating resonantcircuit. Thus, the resonant frequency on the non-radiating resonantcircuit side is able to be increased, and a desired communication bandis able to be obtained.

The antenna device may further include a capacitor that is connectedbetween the first terminal of the second coupling element and theground. Thus, a parasitic capacitance generated between the ground andthe coupling circuit by insertion of the coupling circuit is able to bereduced, and a change from a matching state in which the couplingcircuit is not mounted is able to be reduced or prevented. In addition,the resonant frequency on the non-radiating resonant circuit side isable to be increased, and a desired communication band or communicationcharacteristic is able to be obtained.

The antenna device may further include a second coupling circuitincluding a third coupling element and a fourth coupling element, thethird coupling element being connected between the first couplingelement and the feeder circuit, the fourth coupling element beingcoupled to the third coupling element; and a second non-radiatingresonant circuit connected to the fourth coupling element. Thus, thenumber of resonances to be added is able to be increased, and abandwidth is broadened, and accordingly, a domain in which communicationis possible is broadened. If the resonant frequency is the same orsubstantially the same, the impedance matching is improved.

The antenna device may further include a second coupling circuitincluding a third coupling element and a fourth coupling element, thethird coupling element being connected between the second couplingelement and the non-radiating resonant circuit, the fourth couplingelement being coupled to the third coupling element; and a secondnon-radiating resonant circuit connected to the fourth coupling element.With this structure, a plurality of non-radiating resonant circuits areable to be used, and a communication characteristic is improved.

The antenna device may further include a switch connected between thenon-radiating resonant circuit and the ground. This is able to change aresonant frequency added by providing the coupling circuit and thenon-radiating resonant circuit and is able to change matching so as toimprove impedance matching. In addition, the resonant frequency is ableto be changed or matching is able to be changed such that the couplingcircuit and the non-radiating resonant circuit are easily coupled toeach other, thus improving impedance matching.

In a case in which the coupling circuit includes a parasiticcapacitance, the antenna device preferably further includes an inductorthat is connected to the coupling circuit and that reduced or preventeda reactance component generated in the coupling circuit by parallelresonance with the parasitic capacitance. Thus, a reactance componentthat is added by insertion of the coupling circuit is canceled, and achange from a matching state in which the coupling circuit is notmounted is able to be reduced or prevented.

An antenna device according to a preferred embodiment of the presentinvention includes a radiating element to which a feeder circuit isconnected; a coupling circuit including a first coupling element and asecond coupling element, the first coupling element being connectedbetween the radiating element and a ground, the second coupling elementbeing coupled to the first coupling element; and a non-radiatingresonant circuit connected to the second coupling element, in which afrequency characteristic of a return loss of the radiating element isadjusted by a resonant frequency characteristic of the non-radiatingresonant circuit.

With the above-described configuration, the radiating element and thenon-radiating resonant circuit do not interfere with each otherregarding radiation, in which the radiating element is connected to thefirst coupling element of the coupling circuit and the non-radiatingresonant circuit is connected to the second coupling element of thecoupling circuit, and the radiation characteristic of the radiatingelement is not adversely affected. In addition, the frequencycharacteristic of a return loss of the radiating element seen from thefeeder circuit is adjusted by the resonance characteristic of thenon-radiating resonant circuit, and a pole is generated in a desiredfrequency band to broaden the band of the frequency characteristic ofthe antenna. Since a current intensity is particularly high in a portionthat is connected to the ground, the radiating element and thenon-radiating resonant circuit are able to be coupled to each other viathe coupling circuit. In addition, the coupling circuit and thenon-radiating resonant circuit are able to be disposed with a higherdegree of freedom.

Electronic equipment according to a preferred embodiment of the presentinvention includes an antenna device according to a preferredembodiment; the feeder circuit connected to the coupling circuit; and ahousing in which the feeder circuit is accommodated, in which a portionof the radiating element or the entire radiating element is a portion ofthe housing.

With the above configuration, it is not necessary to provide aconductive member or a conductor pattern that is dedicated to theradiating element, and downsizing is able to be achieved. Also inelectronic equipment including a metal housing, the metal housing doesnot block electromagnetic waves.

According to preferred embodiments of the present invention, antennadevices that avoid the issue of interference regarding radiation of tworadiating elements so as to broaden the band and the electronicequipment including the antenna devices are able to be obtained.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating a main configuration of anantenna device 101 according to a first preferred embodiment of thepresent invention and electronic equipment including the antenna device101.

FIG. 2 is a plan view of a main portion of the antenna device 101.

FIG. 3 is a plan view of a position at which a non-radiating resonantcircuit 20 is provided.

FIG. 4 illustrates a configuration of a coupling circuit 30 and acircuit connected thereto.

FIG. 5A is an equivalent circuit diagram of the antenna device 101 in ahigh band. FIG. 5B is an equivalent circuit diagram of the antennadevice 101 in a low band.

FIG. 6 illustrates a frequency characteristic of a return loss of theantenna device 101 and an antenna device of a comparative example.

FIG. 7 is a conceptual diagram illustrating a difference in impedancematching depending on the strength of coupling of the coupling circuit.

FIG. 8 is a perspective view of the coupling circuit 30.

FIG. 9 is exploded plan views illustrating some conductor patternsprovided on layers of the coupling circuit.

FIG. 10 is a circuit diagram of the coupling circuit 30 including fourcoil conductor patterns.

FIG. 11 illustrates a circuit configuration of an antenna device 102according to a second preferred embodiment of the present invention.

FIG. 12 illustrates a circuit configuration of an antenna device 103according to a third preferred embodiment of the present invention.

FIG. 13 illustrates a circuit configuration of an antenna device 104according to a fourth preferred embodiment of the present invention.

FIG. 14 illustrates a circuit configuration of an antenna device 105according to a fifth preferred embodiment of the present invention.

FIG. 15 illustrates a circuit configuration of an antenna device 106Aaccording to a sixth preferred embodiment of the present invention.

FIG. 16 illustrates a circuit configuration of an antenna device 106Baccording to the sixth preferred embodiment of the present invention.

FIG. 17 illustrates a circuit configuration of an antenna device 106Caccording to the sixth preferred embodiment of the present invention.

FIG. 18 illustrates a circuit configuration of an antenna device 106Daccording to the sixth preferred embodiment of the present invention.

FIG. 19A illustrates a circuit configuration of an antenna device 107Aaccording to a seventh preferred embodiment. FIG. 19B illustrates acircuit configuration of an antenna device 107B according to the seventhpreferred embodiment of the present invention.

FIG. 20 is an exploded plan view illustrating conductor patternsprovided on layers of the coupling circuit 30 according to the seventhpreferred embodiment of the present invention.

FIG. 21 is a sectional view of the coupling circuit 30 according to theseventh preferred embodiment of the present invention.

FIG. 22 is a plan view illustrating overlap between a conductor patternL12 and a conductor pattern L21 in particular in the coupling circuit 30according to the seventh preferred embodiment of the present invention.

FIG. 23 is an exploded plan view illustrating conductor patternsprovided on layers of another coupling circuit 30 according to theseventh preferred embodiment of the present invention.

FIG. 24 illustrates a circuit configuration of an antenna device 108according to an eighth preferred embodiment of the present invention.

FIG. 25 illustrates a circuit configuration of an antenna device 109according to a ninth preferred embodiment of the present invention.

FIG. 26 illustrates a circuit configuration of an antenna device 110according to a tenth preferred embodiment of the present invention.

FIGS. 27A and 27B illustrate circuit configurations of antenna devices111A and 111B according to an eleventh preferred embodiment of thepresent invention.

FIG. 28 illustrates a circuit configuration of an antenna device 112according to a twelfth preferred embodiment of the present invention.

FIG. 29 illustrates a circuit configuration of an antenna device 113according to a thirteenth preferred embodiment of the present invention.

FIG. 30 illustrates a circuit configuration of an antenna device 114according to a fourteenth preferred embodiment of the present invention.

FIG. 31A illustrates a circuit configuration of an antenna device 115according to a fifteenth preferred embodiment of the present invention.FIG. 31B illustrates a frequency characteristic of a return loss of theantenna device 115 illustrated in FIG. 31A and an antenna deviceaccording to a comparative example.

FIG. 32 illustrates a circuit configuration of an antenna device 116according to a sixteenth preferred embodiment of the present invention.

FIG. 33 illustrates a circuit configuration of an antenna device 117according to a seventeenth preferred embodiment of the presentinvention.

FIG. 34 illustrates a frequency characteristic of a return loss of theantenna device 117.

FIG. 35 is a circuit diagram of an antenna device 118A according to aneighteenth preferred embodiment of the present invention.

FIG. 36 is a circuit diagram of another antenna device 118B according tothe eighteenth preferred embodiment of the present invention.

FIG. 37 is a circuit diagram of still another antenna device 118Caccording to the eighteenth preferred embodiment of the presentinvention.

FIG. 38 is a plan view of a main portion of an antenna device 119according to a nineteenth preferred embodiment of the present invention.

FIG. 39 is a perspective view of the coupling circuit 30 according tothe nineteenth preferred embodiment of the present invention.

FIG. 40 illustrates a configuration of another coupling circuit 30according to the nineteenth preferred embodiment of the presentinvention and is an exploded plan view illustrating conductor patternsprovided on layers of the coupling circuit 30.

FIG. 41 is a circuit diagram of an antenna device 120 according to atwentieth preferred embodiment of the present invention in which afeeder circuit 1 is connected.

FIG. 42 is an equivalent circuit diagram illustrating a phase shifter 50according to the twentieth preferred embodiment of the present inventionin which an ideal transformer IT and parasitic inductance components areseparately illustrated.

FIG. 43 illustrates a frequency characteristic of a phase shift amountof the phase shifter 50.

FIG. 44A is a circuit diagram of the antenna device illustrated in thefirst preferred embodiment of the present invention, which does notinclude the phase shifter 50, and FIG. 44B illustrates impedance locirepresenting, on a Smith chart, impedances when seeing the antennadevice from the feeder circuit 1.

FIG. 45A is a circuit diagram of an antenna device to which the phaseshifter 50 is added. FIG. 45B illustrates impedance loci representing,on a Smith chart, impedances when seeing the antenna device from thefeeder circuit 1.

FIG. 46A is a circuit diagram of an antenna device including animpedance matching capacitor C5. FIG. 46B illustrates an impedance locusrepresenting, on a Smith chart, an impedance when seeing the antennadevice from the feeder circuit 1.

FIG. 47 illustrates a frequency characteristic of a return loss of theantenna devices illustrated in FIG. 44A and FIG. 46A and an antennadevice according to a comparative example.

FIG. 48 is an external perspective view of the phase shifter 50.

FIG. 49 is a plan view of layers in the phase shifter 50.

FIG. 50 is a sectional view of the phase shifter 50.

FIG. 51 is a plan view illustrating a portion of a metal housing ofelectronic equipment according to a twenty-first preferred embodiment ofthe present invention.

FIGS. 52A and 52B are perspective views illustrating portions of metalhousings of different pieces of electronic equipment according to thetwenty-first preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A plurality of preferred embodiments of the present invention will bedescribed below with reference to specific examples and the drawings.The same reference numerals denote the same or substantially the sameportions and elements in the drawings. Considering the explanation ofmain points and to facilitate understanding, the preferred embodimentsare separately illustrated for convenience. However, portions andelements illustrated in different preferred embodiments may be replacedor combined. In second and subsequent preferred embodiments, adescription of portions and elements that are common to a firstpreferred embodiment will be omitted, and only different points will bedescribed. In particular, the same or substantially the sameadvantageous effects obtained by the same or substantially the sameconfiguration will not be repeated in the preferred embodiments.

The “antenna device” illustrated in the preferred embodiments isapplicable to one that transmits signals or one that receives signals.Even in a case in which the “antenna device” is described as an antennathat radiates electromagnetic waves, the antenna device is not limitedto a source that generates the electromagnetic waves. Also in a case ofreceiving an electromagnetic wave that is generated by acommunication-partner antenna device, that is, even when thetransmission and reception are reversed, the same or substantially thesame advantageous effects are produced.

First Preferred Embodiment

FIG. 1 is a perspective view illustrating a main configuration of anantenna device 101 according to the first preferred embodiment andelectronic equipment including the antenna device 101. FIG. 2 is a planview of a main portion of the antenna device 101.

A metal housing of the electronic equipment includes a radiating element10, which is an end portion of the metal housing, and a metal housingmain portion 40. The metal housing main portion 40 includes a planarportion 41 and side surface portions 42 and 43.

The antenna device 101 includes the radiating element 10, anon-radiating resonant circuit 20, and the coupling circuit 30.

The radiating element 10 is defined by the end portion of the metalhousing, and includes an end surface portion 11 and side surfaceportions 12 and 13. An end portion of the side surface portion 12 isconnected to a ground (is grounded) of a circuit substrate 6 via aninductor 8. Although an end portion of the side surface portion 13 isopen, a parasitic capacitance C is generated between this open end andthe ground. Note that a connector 7, such as a USB, for example, ismounted on the circuit substrate 6, and an opening for the connector 7is provided in the end surface portion 11. However, the connector 7 isnot a component of the antenna device 101.

The circuit substrate 6 includes a ground region GZ in which a groundelectrode GND is provided and a non-ground region NGZ in which a groundelectrode is not provided. The end portion of the metal housing, whichdefines the radiating element 10, is located on the non-ground regionside. In the non-ground region NGZ of the circuit substrate 6, thenon-radiating resonant circuit is defined by a conductor pattern. Alsoin the non-ground region NGZ of the circuit substrate 6, a feeding line9 that connects the coupling circuit 30 and the radiating element 10 toeach other is provided.

As illustrated in FIG. 2, the non-radiating resonant circuit 20 isdefined by a linear conductor pattern including a returning portion 20FBalong the linear conductor pattern. In this manner, since the linearconductor pattern including a returning portion along the linearconductor pattern is provided, the non-radiating resonant circuit 20 isprovided in a small area, and an electric length that is necessary forresonance is able to be obtained. In addition, in the present preferredembodiment, a first linear conductor pattern portion 21 extending fromthe coupling circuit 30 and a second linear conductor pattern portion 22that returns to a side away from the radiating element 10 are included.With this structure, since a portion close to the radiating element 10(the end surface portion 11 in particular) is short, and extendingdirections are opposite to each other, substantial coupling with theradiating element 10 (the end surface portion 11 in particular) is weak.This reduces or prevents unnecessary coupling between the non-radiatingresonant circuit 20 and the radiating element 10.

Note that the second linear conductor pattern portion 22 is preferablywider than the first linear conductor pattern portion 21. Thus, aresonant bandwidth is able to be broadened.

FIG. 3 is a plan view illustrating a position at which the non-radiatingresonant circuit 20 is provided. The radiating element 10 is defined bya conductive member (the end surface portion 11 and the side surfaceportions 12 and 13) that includes three sides in a plan view, and thenon-radiating resonant circuit is surrounded by a radiating elementformation region 10Z surrounded by the three sides of the radiatingelement 10 in a plan view. The entire or substantially the entirenon-radiating resonant circuit 20 does not have to be provided withinthe radiating element formation region 10Z, and a about half or more ofthe non-radiating resonant circuit 20 is preferably included within theradiating element formation region 10Z. Since the non-radiating resonantcircuit 20 is not used as a radiating element, the non-radiatingresonant circuit 20 is preferably “non-radiating”. Thus, in a case inwhich the non-radiating resonant circuit 20 is surrounded by the threesides of the conductive member in a plan view and about half or more ofthe non-radiating resonant circuit 20 is included within the radiatingelement formation region 10Z, the non-radiating resonant circuit 20 isshielded by the radiating element 10. This increases a non-radiatingproperty of the non-radiating resonant circuit 20 seen from a distance.

FIG. 4 illustrates a configuration of the coupling circuit 30 and acircuit connected thereto. The coupling circuit includes a firstcoupling element 31 and a second coupling element 32 that is coupled tothe first coupling element 31, and a transformer is defined by the firstcoupling element 31 and the second coupling element 32. The firstcoupling element 31 and the second coupling element 32 have smallinductances, each of which is preferably, for example, about 10 nH orless. The radiating element 10 and the non-radiating resonant circuit 20are coupled to each other via the coupling circuit 30 preferably with acoupling coefficient of, for example about 0.5 or more, and morepreferably with a coupling coefficient of, for example, about 0.8 ormore. When the inductance of a coupling element is smaller, an influenceon a circuit characteristic and a radiation characteristic of theradiating element 10 is able to be further reduced or prevented. Whenthe coupling coefficient is higher, the radiating element 10 and thenon-radiating resonant circuit 20 are able to be more electricallyconnected to each other, and a resonance point is able to be added toonly a frequency at which the non-radiating resonant circuit 20 morelargely contributes to resonance. In this manner, by configuring atransformer in which electromagnetic field coupling is produced betweenthe first coupling element 31 and the second coupling element 32, acoupling circuit with a high coupling coefficient between the firstcoupling element 31 and the second coupling element 32 is provided, anda resonance characteristic of the non-radiating resonant circuit 20 whenviewing the radiating element 10 from a feeder circuit 1 is likely to beshown.

The first coupling element 31 is connected between the radiating element10 and the feeder circuit 1. A first end of the second coupling element32 is connected to the non-radiating resonant circuit 20, and a secondend thereof is connected to the ground (is grounded) of the circuitsubstrate 6.

With the electronic equipment according to the present preferredembodiment, the metal portion of the housing that accommodates thefeeder circuit is used as the radiating element, and thus, it isunnecessary to provide a conductive member or a conductor patterndedicated to the radiating element, thus reducing the size of theelectronic equipment. In addition, also in electronic equipmentincluding a metal housing, the metal housing does not blockelectromagnetic waves.

FIG. 5A is an equivalent circuit diagram of the antenna device 101 in ahigh band. In a high band (e.g., 1.6 GHz to 2.3 GHz), the inductor 8(see FIG. 2 and FIG. 4) has a predetermined high impedance, and a tip ofthe radiating element 10 is equivalently open. In this state, theradiating element 10 serves as a monopole antenna that resonates at ¾wavelengths or (2n+1)/4 wavelengths (n is a natural number).

FIG. 5B is an equivalent circuit diagram of the antenna device 101 in alow band. In a low band (e.g., about 700 MHz to about 900 MHz), theinductor 8 has a predetermined inductance, and the tip of the radiatingelement 10 is grounded via the inductor 8. In this state, the radiatingelement 10 defines and functions as a loop antenna of one wavelength oran integer multiple thereof.

A series circuit including an inductor L20 and a capacitor C20illustrated in FIGS. 5A and 5B is an element that represents anequivalent circuit in which the non-radiating resonant circuit 20 issimply illustrated as a lumped constant circuit. The non-radiatingresonant circuit 20 defines and functions as an open stub that resonatesat a predetermined frequency at about ¾ wavelengths or about (2n+1)/4wavelengths (n is a natural number), for example. Thus, the inductor L20and the capacitor C20 are used in FIGS. 5A and 5B. The non-radiatingresonant circuit 20 resonates in, for example, a frequency band whosecenter is about 2.1 GHz, for example. Note that in the present preferredembodiment, since the non-radiating resonant circuit 20 has a shape inwhich the linear conductor pattern is returned, a standing wave is notprovided in the linear conductor pattern compared with a simple straightline conductor pattern, and a Q value of resonance as a resonancecircuit is relatively small.

FIG. 6 illustrates a frequency characteristic of a return loss of theantenna device 101 and an antenna device of a comparative example. InFIG. 6, a return loss characteristic RL1 is a return loss of the antennadevice 101 according to the present preferred embodiment, and a returnloss characteristic RL2 is a return loss of the antenna device accordingto the comparative example. The antenna device according to thecomparative example is an antenna device in which the coupling circuit30 and the non-radiating resonant circuit 20 are not included. In eitherantenna device, a pole is generated at a center frequency F1 of a lowband (e.g., about 700 MHz to about 900 MHz). This is due to theresonance characteristic of the loop antenna illustrated in FIG. 5B.Another pole is generated at a frequency F2 (e.g., around 1.75 GHz).This is due to ¾ wavelength resonance of the monopole antennaillustrated in FIG. 5A. Another pole is generated at a frequency F3(e.g., around 2.3 GHz). This is due to 5/4 wavelength resonance of themonopole antenna illustrated in FIG. 5A.

Note that it is preferable that a length “r1” of a line between thefirst coupling element 31 and the feeder circuit 1 illustrated in FIG. 4and a length “r2” of a line between an end portion of the secondcoupling element 32 and the ground are less than about ⅛ wavelength ofthe resonant frequency, for example. The wavelength here may mean aneffective wavelength considering a wavelength shortening effect of amagnetic body or a dielectric. The threshold is set to about “⅛wavelength” because it is practical until a condition at which ⅛wavelength current becomes 1/√2, in other words, a power that is able tobe transmitted is approximately halved, is satisfied.

Here, FIG. 7 illustrates a conceptual diagram of a difference inimpedance matching depending on the strength of the coupling. In FIG. 7,loci T0, T1, and T2 are impedance loci representing, on a Smith chart,impedances when seeing the antenna device 101 from the feeder circuit 1.Locus T0 is a characteristic in a state in which the coupling circuit 30and the non-radiating resonant circuit 20 are not provided, locus T1 isa characteristic in a state in which the first coupling element 31 andthe second coupling element 32 of the coupling circuit 30 areappropriately coupled to each other, and locus T2 is a characteristic ina state in which the coupling between the first coupling element 31 andthe second coupling element 32 of the coupling circuit 30 is too strong.

In this manner, when the coupling between the first coupling element 31and the second coupling element 32 of the coupling circuit 30 is toostrong, the input impedance seen from the feeder circuit deviates fromthe impedance (e.g., about 50Ω) on the feeder circuit (and transmissionline) side. Therefore, it is important that the first coupling element31 and the second coupling element 32 of the coupling circuit 30 areappropriately coupled to each other. The length “r1” of the line betweenthe first coupling element 31 and the feeder circuit 1 and the length“r2” of the line between the end portion of the second coupling element32 and the ground are set within a range of less than about ⅛ wavelengthof the resonant frequency, and thus, the coupling by the couplingcircuit 30 is able to be appropriately set.

In the antenna device 101 according to the present preferred embodiment,another pole is generated at a frequency F0 (e.g., around 2.1 GHz). Thisis due to the resonance characteristic of the non-radiating resonantcircuit 20. That is, since the non-radiating resonant circuit 20resonates in a frequency band whose center frequency is about 2.1 GHz,for example, the pole is generated at about 2.1 GHz in the frequencycharacteristic of a return loss of the antenna device 101 seen from thefeeder circuit 1. With the antenna device 101 according to the presentpreferred embodiment, a high-band application frequency band isbroadened from about 1.6 GHz to about 2.3 GHz.

In the low band, the non-radiating resonant circuit 20 does notresonate, and the return loss characteristic in the low band is notinfluenced. That is, the non-radiating resonant circuit 20 influencesthe return loss characteristic seen from the feeder circuit 1 in, forexample, a frequency band of about 1.6 GHz or higher, and thenon-radiating resonant circuit 20 has substantially no influence in afrequency band lower than that.

The return loss characteristic at around the frequency F0 is determinedby the resonance characteristic of the non-radiating resonant circuit20, and accordingly, the return loss characteristic at about thefrequency F0 can be determined as appropriate by the shape of theconductor pattern that constitutes the non-radiating resonant circuit.In the present preferred embodiment, since the non-radiating resonantcircuit 20 is defined by the linear conductor pattern that includes areturning portion along the linear conductor pattern, the sharpness ofresonance of the non-radiating resonant circuit 20 is degraded, and thenon-radiating resonant circuit 20 is able to attenuate a reflectioncoefficient in a wide band including the band in which the polegenerated at the frequency F0 and its periphery.

Note that the non-radiating resonant circuit 20 that defines andfunctions as an open stub is provided independently or substantiallyindependently of the radiating element 10. Thus, there is no influenceon a low band, unlike in a case in which a stub is provided in theradiating element, for example.

Next, a configuration of the coupling circuit 30 will be described. FIG.8 is a perspective view of the coupling circuit 30, and FIG. 9 is anexploded plan view illustrating conductor patterns provided on layers ofthe coupling circuit.

The coupling circuit 30 included in the antenna device according to thepresent preferred embodiment is preferably, for example, a rectangularor substantially rectangular parallelepiped chip component to be mountedon the circuit substrate 6. In FIG. 8, an external configuration of thecoupling circuit 30 and an internal structure thereof are separatelyillustrated. The external configuration of the coupling circuit 30 isrepresented by a two-dotted-and-dashed line. On an outer surface of thecoupling circuit 30, a feeder circuit connection terminal PF, aradiating element connection terminal PA, a ground terminal PG, and anon-radiating resonant circuit connection terminal PS are provided. Inaddition, the coupling circuit 30 includes a first surface MS1 and asecond surface MS2 that is opposed to the first face. In the presentpreferred embodiment, the first surface MS1 is a mount surface, and thissurface faces a circuit substrate. On a top surface (second surface)that is opposed to the mount surface (first surface) MS1, a directiondiscrimination mark DDM is provided. This direction discrimination markDDM is used to detect a direction of a chip component when, for example,the coupling circuit 30 is mounted as the chip component on a circuitsubstrate by a mounter.

Inside the coupling circuit 30, a first conductor pattern L11, a secondconductor pattern L12, a third conductor pattern L21, and a fourthconductor pattern L22 are provided. The first conductor pattern L11 andthe second conductor pattern L12 are connected to each other by aninterlayer connection conductor V1. The third conductor pattern L21 andthe fourth conductor pattern L22 are connected to each other by aninterlayer connection conductor V2. Note that FIG. 8 illustratesinsulating materials S11, S12, S21, and S22, on which the respectiveconductor patterns are provided, separately in a stacking direction.These insulating materials S11, S12, S21, and S22 may preferably be anon-magnetic ceramic multi-layer body made of, for example, LTCC (LowTemperature Co-fired Ceramics) or other suitable material, or may be aresin multi-layer body preferably made of, for example, a resinmaterial, such as polyimide or liquid crystal polymer. In this manner,since the material layers are non-magnetic (not a magnetic ferrite), itis possible to use the material layers for a coupling circuit even in ahigh frequency band exceeding several hundreds of MHz.

Each of the conductor patterns and the interlayer connection conductorsis preferably made of, for example, a conductor material including Ag orCu as a main component and having a small resistivity. In a case inwhich the material layers are ceramic, for example, the conductorpatterns and the interlayer connection conductors are formed by screenprinting and firing of a conductive paste including Ag or Cu as a maincomponent. In a case in which the material layers are resin, forexample, the conductor patterns and the interlayer connection conductorsare patterned by etching or other suitable method of a metal foil, suchas an Al foil or a Cu foil, for example.

As illustrated in FIG. 9, the first conductor pattern L11, the secondconductor pattern L12, the third conductor pattern L21, and the fourthconductor pattern L22 are provided in this order from a layer close tothe mount surface. A first end of the first conductor pattern L11 isconnected to the radiating element connection terminal PA, and a secondend thereof is connected to a first end of the second conductor patternL12 via the interlayer connection conductor V1. A second end of thesecond conductor pattern L12 is connected to the feeder circuitconnection terminal PF. In addition, a first end of the third conductorpattern L21 is connected to a non-radiating resonant circuit connectionterminal PS, and a second end of the third conductor pattern L21 isconnected to a first end of the fourth conductor pattern L22 via theinterlayer connection conductor V2. A second end of the fourth conductorpattern L22 is connected to the ground terminal PG.

In addition, a winding direction of the first coupling element 31 fromthe feeder circuit connection terminal PF to the radiating elementconnection terminal PA and a winding direction of the second couplingelement 32 from the non-radiating resonant circuit connection terminalPS to the ground terminal PG are opposite to each other. That is, amagnetic field (magnetic flux) generated when current flows in the firstcoupling element 31 from the feeder circuit connection terminal PF tothe radiating element connection terminal PA and a magnetic field(magnetic flux) generated when current flows in the second couplingelement 32 from the non-radiating resonant circuit connection terminalPS to the ground terminal PG weaken each other. Here, when the radiatingelement connection terminal PA resonates as a monopole antenna, thefirst coupling element 31 and the second coupling element 32 haveopposite polarities in the coupling circuit 30 that is connected via thefeeder circuit 1 and the ground electrode GND. Current flows in thefirst coupling element 31 from the feeder circuit connection terminal PFto the radiating element connection terminal PA, and current flows inthe second coupling element 32 from the non-radiating resonant circuitconnection terminal PS to the ground terminal PG. Magnetic fields(magnetic fluxes) that are generated weaken each other. Thus, a mutualinductance due to the coupling between the first coupling element 31 andthe second coupling element 32 decreases the inductances of the firstcoupling element 31 and the second coupling element 32, so as to havelittle influence on the circuit characteristic and the radiationcharacteristic of the radiating element 10.

FIG. 10 is a circuit diagram of the coupling circuit 30 including thefour coil conductor patterns. The second conductor pattern L12 and thefirst conductor pattern L11 are connected in series to define the firstcoupling element 31. Similarly, the fourth conductor pattern L22 and thethird conductor pattern L21 are connected in series to define the secondcoupling element 32. The second conductor pattern L12 and the thirdconductor pattern L21 are adjacent to each other in the thicknessdirection, and the magnetic field coupling between the second conductorpattern L12 and the third conductor pattern L21 is particularly strong.Thus, the second conductor pattern L12 and the third conductor patternL21 are adjacent to each other in FIG. 10. Obviously, magnetic fieldcoupling is established between the second conductor pattern L12 and thefourth conductor pattern L22 and between the first conductor pattern L11and the third conductor pattern L21.

In the example illustrated in FIG. 9, a capacitor formation conductorpattern C11 is provided in a portion of the second conductor patternL12, and a capacitor formation conductor pattern C12 is provided in aportion of the third conductor pattern L21. Accordingly, as illustratedin FIG. 10, a capacitor C1 is provided between a middle of the secondconductor pattern L12 and the non-radiating resonant circuit connectionterminal PS. The capacitor C1 defines and functions as an impedancematching circuit between the feeder circuit 1 and the non-radiatingresonant circuit 20.

Second Preferred Embodiment

FIG. 11 illustrates a circuit configuration of an antenna device 102according to the second preferred embodiment of the present invention.In the antenna device 102, an inductor 35 is connected (inserted)between the second coupling element 32 of the coupling circuit 30 andthe non-radiating resonant circuit 20. The remaining configuration isthe same as or similar to that of the circuit illustrated in FIG. 4 inthe first preferred embodiment.

According to the present preferred embodiment, since the inductor 35 isprovided to a portion at which current is low, while a change in thecoupling of the coupling circuit 30 is reduced or prevented, theresonant frequency of the non-radiating resonant circuit 20 is able tobe decreased, and a desired communication band is able to be obtained.Alternatively, while the resonant frequency is maintained, the length ofthe non-radiating resonant circuit 20 is able to be reduced, and thusthe area used is able to be reduced.

Note that the inductor 35 may also be integrated with the couplingcircuit 30. However, it is preferable that the inductor 35 is notcoupled to the first coupling element 31.

Third Preferred Embodiment

FIG. 12 illustrates a circuit configuration of an antenna device 103according to a third preferred embodiment of the present invention. Inthe antenna device 103, the inductor 35 is connected (inserted) betweenthe second coupling element 32 of the coupling circuit 30 and theground. The remaining configuration is the same as or similar to that ofthe circuit illustrated in FIG. 4 in the first preferred embodiment.

When the coupling circuit 30 is added to the antenna device, a parasiticcapacitance is generated between the ground and the coupling circuit 30.According to the present preferred embodiment, resonance between theinductor 35 and the parasitic capacitance reduce or prevent a reactancecomponent. Therefore, in a frequency band in which an antennacharacteristic is not to be changed by addition of the coupling circuit30 to the antenna device, by providing the inductor 35 with such aninductance as to resonate with the parasitic capacitance, a change froma matching state in which the coupling circuit 30 is not mounted is ableto be reduced or prevented.

In addition, the inclusion of the inductor 35 is able to decrease theresonant frequency of the non-radiating resonant circuit 20, and adesired communication band or communication characteristic is able to beobtained. Alternatively, while the resonant frequency is maintained, thelength of the antenna is able to be reduced, and the area used is ableto be reduced.

Note that the inductor 35 may also be integrated with the couplingcircuit 30. However, it is preferable that the inductor 35 is notcoupled to the first coupling element 31.

Fourth Preferred Embodiment

FIG. 13 illustrates a circuit configuration of an antenna device 104according to a fourth preferred embodiment of the present invention. Inthe antenna device 104, a capacitor 36 is connected (inserted) betweenthe second coupling element 32 of the coupling circuit 30 and thenon-radiating resonant circuit 20. The remaining configuration is thesame as or similar to that of the circuit illustrated in FIG. 4 in thefirst preferred embodiment.

According to the present preferred embodiment, the resonant frequency onthe non-radiating resonant circuit side is able to be increased, and adesired communication band is able to be obtained.

Note that the capacitor 36 may be integrated with the coupling circuit30.

Fifth Preferred Embodiment

FIG. 14 illustrates a circuit configuration of an antenna device 105according to a fifth preferred embodiment of the present invention. Inthe antenna device 105, the capacitor 36 is connected (inserted) betweenthe second coupling element 32 of the coupling circuit 30 and theground. The remaining configuration is the same as or similar to that ofthe circuit illustrated in FIG. 4 in the first preferred embodiment.

According to the present preferred embodiment, a parasitic capacitancegenerated between the ground and the coupling circuit 30 by inclusion ofthe coupling circuit 30 is able to be reduced (combined capacitance isable to be reduced), and a change from a matching state in which thecoupling circuit 30 is not provided is able to be reduced or prevented.In addition, the resonant frequency of the non-radiating resonantcircuit 20 is able to be increased, and a desired communication band orcommunication characteristic is able to be obtained.

Note that the capacitor 36 may be integrated with the coupling circuit30.

Sixth Preferred Embodiment

FIG. 15 illustrates a circuit configuration of an antenna device 106Aaccording to a sixth preferred embodiment of the present invention. Inthe antenna device 106A, the inductor 35 is connected (inserted) betweenthe first coupling element 31 of the coupling circuit 30 and theradiating element 10. The remaining configuration is the same as orsimilar to that of the circuit illustrated in FIG. 4 in the firstpreferred embodiment.

With the configuration of the antenna device 106A, the first couplingelement 31 is closer to the feeder circuit 1, at which the current isstrong, than the inductor 35 is. Thus, while a power ratio to besupplied to the non-radiating resonant circuit 20 is maintained, theresonant frequency of the radiating element 10 is able to be changed,and a level of impedance matching is able to be adjusted. In addition, aself-resonant frequency that is determined by the inductances of thefirst coupling element 31 and the second coupling element 32 and theparasitic capacitance generated between the first coupling element 31and the second coupling element 32 is unlikely to be decreased, andthus, the self-resonant frequency does not adversely affect the use in acommunication frequency band. That is, in a state of self-resonance,energy in the frequency band falls to the ground and is not radiated.However, in a state in which the self-resonant frequency is higher thanthe communication frequency band, such a problem does not arise.

FIG. 16 illustrates a circuit configuration of an antenna device 106Baccording to the sixth preferred embodiment. In the antenna device 106B,the inductor 35 is connected (inserted) between the first couplingelement 31 of the coupling circuit 30 and the feeder circuit 1. Theremaining configuration is the same as or similar to that of the circuitillustrated in FIG. 4 in the first preferred embodiment.

With the configuration of the antenna device 106B, since the firstcoupling element 31 of the coupling circuit 30 is disposed to a side atwhich current is weaker than that at the position of the inductor 35,compared with a case in which the inductor is disposed between theradiating element 10 and the first coupling element 31, it is possibleto adjust the level of impedance matching as appropriate in resonance(resonant frequency) added by the coupling circuit 30 and thenon-radiating resonant circuit 20. Specifically, it is possible to avoida situation in which an input impedance excessively changes and theimpedance is no longer matched.

In addition, the inclusion of the inductor 35 is able to decrease theself-resonant frequency of the coupling circuit 30, and thus, by settingthe self-resonant frequency to a frequency band that is not desired tobe radiated, unnecessary radiation is able to be reduced or prevented.

FIG. 17 illustrates a circuit configuration of an antenna device 106Caccording to the sixth preferred embodiment. In the antenna device 106C,the capacitor 36 is connected (inserted) between the first couplingelement 31 of the coupling circuit 30 and the radiating element 10. Theremaining configuration is the same as or similar to that of the circuitillustrated in FIG. 4 in the first preferred embodiment.

With the configuration of the antenna device 106C, by the capacitance ofthe capacitor 36, the resonant frequency of the radiating element 10 isable to be adjusted, and the level of impedance matching is able to beadjusted.

FIG. 18 illustrates a circuit configuration of an antenna device 106Daccording to the sixth preferred embodiment. In the antenna device 106D,the capacitor 36 is connected (inserted) between the first couplingelement 31 of the coupling circuit 30 and the feeder circuit 1. Theremaining configuration is the same as or similar to that of the circuitillustrated in FIG. 4 in the first preferred embodiment.

With the configuration of the antenna device 106D, by the capacitance ofthe capacitor 36, the resonant frequency of the radiating element 10 isable to be adjusted, and the level of impedance matching is able to beadjusted. In addition, since the capacitor 36 is disposed between thefeeder circuit 1 and the first coupling element 31, a parasiticcapacitance generated between the first coupling element 31 and thesecond coupling element 32 and the capacitor 36 are connected in series.Accordingly, a combined capacitance included in a self-resonant circuitsystem is decreased, and the self-resonant frequency is increased. Thus,the self-resonant frequency is able to be excluded from thecommunication band to be used.

Seventh Preferred Embodiment

FIG. 19A illustrates a circuit configuration of an antenna device 107Aaccording to a seventh preferred embodiment of the present invention,and FIG. 19B illustrates a circuit configuration of an antenna device107B according to the seventh preferred embodiment. The configuration ofthese antenna devices 107A and 107B is the same as or similar to that ofthe circuit illustrated in FIG. 4 in the first preferred embodiment.However, when a self-inductance of the first coupling element 31 of thecoupling circuit 30 is represented as L1 and a self-inductance of thesecond coupling element 32 is represented as L2, the first couplingelement 31 and the second coupling element 32 of the coupling circuit 30preferably have a relationship of L2>L1 in the antenna device 107A, anda relationship of L2<L1 in the antenna device 107B. With therelationship of L2>L1, compared with a case in which L1=L2, the resonantfrequency of the non-radiating resonant circuit 20 is able to bedecreased. Alternatively, when comparison is made at the same resonantfrequency, the non-radiating resonant circuit 20 is able to beshortened.

In addition, when L2>L1, compared with a configuration in which theinductor is connected (added) to the second coupling element 32 outsidethe coupling circuit 30, the entire or substantially the entire secondcoupling element 32 with a relatively large self-inductance contributesto the coupling with the first coupling element 31. Thus, a power ratioto be supplied to the non-radiating resonant circuit 20 is able to beincreased.

In addition, when L2<L1, compared with a configuration in which theinductor is connected (added) to the first coupling element 31 outsidethe coupling circuit 30, the entire or substantially the entire firstcoupling element 31 with a relatively large self-inductance contributesto the coupling with the second coupling element 32. Thus, a power ratioto be supplied to the non-radiating resonant circuit 20 is able to beincreased.

FIG. 20 is an exploded plan view illustrating conductor patternsprovided on layers of the coupling circuit 30 according to the presentpreferred embodiment. The coupling circuit 30 included in an antennadevice according to the present preferred embodiment is preferably, forexample, a rectangular or substantially rectangular parallelepiped chipcomponent to be mounted on a circuit substrate.

On insulating materials S11, S12, S21, S22, and S23, conductor patternsL11, L12, L21, L22, and L23 are respectively provided. A first end ofthe conductor pattern L11 is connected to the radiating elementconnection terminal PA, and a second end thereof is connected to a firstend of the conductor pattern L12 via the interlayer connection conductorV1. A second end of the conductor pattern L12 is connected to the feedercircuit connection terminal PF. A first end of the conductor pattern L21is connected to the non-radiating resonant circuit connection terminalPS, and a second end thereof is connected to a first end of theconductor pattern L22 via an interlayer connection conductor V21. Asecond end of the conductor pattern L22 is connected to a first end ofthe conductor pattern L23 via an interlayer connection conductor V22. Asecond end of the conductor pattern L23 is connected to the groundterminal PG.

FIG. 21 is a sectional view of the coupling circuit 30. FIG. 22 is aplan view illustrating overlap between the conductor pattern L12 and theconductor pattern L21 in particular. A coil opening or a coil diameterof the conductor patterns L11 and L12 of the first coupling element 31is smaller than a coil opening or a coil diameter of the conductorpatterns L21, L22, and L23 of the second coupling element 32. Inaddition, portions of the conductor patterns L11 and L12 and theconductor patterns L21, L22, and L23 overlap with each other. In theexample illustrated in FIG. 21 and FIG. 22, about ½ of the width of theconductor patterns is overlapped along the entire or substantially theentire circumference.

FIG. 23 is an exploded plan view illustrating conductor patternsprovided on layers of another coupling circuit 30 according to theseventh preferred embodiment. The shape and size of the conductorpatterns differ from those in the example illustrated in FIG. 20. Amongthe conductor patterns of the coupling circuit illustrated in FIG. 23, acoil outer diameter of the conductor patterns L11 and L12 of the firstcoupling element 31 is smaller than a coil inner diameter of theconductor patterns L21, L22, and L23 of the second coupling element 32.

With the configuration illustrated in FIG. 20 to FIG. 23, a parasiticcapacitance generated between the conductor patterns (L11 and L12) ofthe first coupling element 31 and the conductor patterns (L21, L22, andL23) of the second coupling element 32 is reduced or prevented.Accordingly, the self-resonant frequency determined by the inductancesof the first coupling element 31 and the second coupling element 32 andthe above parasitic capacitance is increased, and the self-resonantfrequency is able to be excluded from the communication band to be used.In addition, even if the conductor patterns (L11 and L12) of the firstcoupling element 31 and the conductor patterns (L21, L22, and L23) ofthe second coupling element 32 are misaligned in a plane direction (X-Yplane direction illustrated in FIG. 22), the portion at which the coilopening of the first coupling element 31 and the coil opening of thesecond coupling element 32 overlap with each other is consistentlymaintained. Accordingly, only a small change in the coupling degree ofmagnetic field coupling between the first coupling element 31 and thesecond coupling element 32 is produced by plane-direction misalignmentof the conductor patterns (L11 and L12) constituting the first couplingelement 31 and the conductor patterns (L21, L22, and L23) constitutingthe second coupling element 32.

The examples in FIG. 20 and FIG. 23 are both examples of a couplingcircuit in which the relationship L1<L2 is satisfied. When L1>L2, thefirst coupling element 31 may be defined by conductor patterns having arelatively large coil opening.

Note that FIG. 20 and FIG. 23 illustrate examples in which an influencedue to misalignment of the conductor patterns (L11 and L12) of the firstcoupling element 31 and the conductor patterns (L21, L22, and L23) ofthe second coupling element 32 is reduced. Similarly, an influence dueto plane-direction misalignment of the conductor patterns of the firstcoupling element 31 and an influence due to plane-direction misalignmentof the conductor patterns of the second coupling element 32 is able tobe reduced. For example, coil openings or coil diameters of theconductor patterns L11 and L12 that are adjacent to each other in thestacking direction may differ from each other, and portions of linewidth thereof may overlap with each other in the structure. Similarly,for example, coil openings or coil diameters of the conductor patternsL21, L22, and L23 that are adjacent to one another in the stackingdirection may differ from one another, and portions of line widththereof may overlap with one another in the structure.

Eighth Preferred Embodiment

FIG. 24 illustrates a circuit configuration of an antenna device 108according to an eighth preferred embodiment of the present invention.The antenna device 108 includes a first coupling circuit 30A, a secondcoupling circuit 30B, a first non-radiating resonant circuit 20A, and asecond non-radiating resonant circuit 20B. The second coupling circuit30B includes a third coupling element 33 and a fourth coupling element34 that are coupled to each other. The third coupling element 33 of thesecond coupling circuit 30B is connected between the first couplingelement 31 and the feeder circuit 1. The first non-radiating resonantcircuit 20A is connected to the second coupling element 32, and thesecond non-radiating resonant circuit 20B is connected to the fourthcoupling element 34. The remaining configuration is the same as orsimilar to that of the circuit illustrated in FIG. 4 in the firstpreferred embodiment.

A resonant frequency of the first non-radiating resonant circuit 20A anda resonant frequency of the second non-radiating resonant circuit 20Bdiffer from each other, and thus, a plurality of poles in accordancewith these resonant frequencies are generated, and a communicationbandwidth is broadened. In addition, if the resonant frequency of thefirst non-radiating resonant circuit 20A and the resonant frequency ofthe second non-radiating resonant circuit 20B are equal or substantiallyequal to each other, the poles generated in the two non-radiatingresonant circuits become deeper, and impedance matching in thisfrequency band is improved.

Ninth Preferred Embodiment

FIG. 25 illustrates a circuit configuration of an antenna device 109according to a ninth preferred embodiment of the present invention. Theantenna device 109 includes the first coupling circuit 30A, the secondcoupling circuit 30B, the first non-radiating resonant circuit 20A, andthe second non-radiating resonant circuit 20B. The second couplingcircuit 30B includes the third coupling element 33 and the fourthcoupling element 34 that are coupled to each other.

The third coupling element 33 is connected between the second couplingelement 32 and the first non-radiating resonant circuit 20A. The firstnon-radiating resonant circuit 20A is connected to the second couplingelement 32, and the second non-radiating resonant circuit 20B isconnected to the fourth coupling element 34. The remaining configurationis the same as or similar to that of the circuit illustrated in FIG. 4in the first preferred embodiment.

In the present preferred embodiment, the resonant frequency of the firstnon-radiating resonant circuit 20A and the resonant frequency of thesecond non-radiating resonant circuit 20B are equal or substantiallyequal to each other, and thus, the poles generated in the twonon-radiating resonant circuits become deeper, and impedance matching inthis frequency band is improved.

Tenth Preferred Embodiment

FIG. 26 is a circuit diagram of an antenna device 110 according to atenth preferred embodiment of the present invention. The antenna device110 includes a switch 37 connected between the non-radiating resonantcircuit 20 and the ground. The antenna device 110 also includes a switch38 connected between the radiating element 10 and the ground. Theremaining configuration is the same as or similar to that of the circuitillustrated in FIG. 4 in the first preferred embodiment.

The switches 37 and 38 are switched independently or in association witheach other. By changing the frequency of a pole generated by providingthe coupling circuit 30 and the non-radiating resonant circuit 20 inaccordance with the state of the switch 37, or by changing a matchingstate, the impedance matching is able to be improved. In addition, bychanging the resonant frequency of the non-radiating resonant circuit 20or by changing the impedance matching state between the coupling circuit30 and the non-radiating resonant circuit 20 so as to make thenon-radiating resonant circuit 20 be coupled easily to the feedercircuit 1 via the coupling circuit 30, the impedance matching is able tobe improved.

In addition, in accordance with the state of the switch 38, thefrequency of a pole generated by resonance of the radiating element 10is able to be changed.

Eleventh Preferred Embodiment

FIGS. 27A and 27B illustrate circuit configurations of antenna devices111A and 111B according to an eleventh preferred embodiment of thepresent invention. In the examples in both of FIGS. 27A and 27B,parasitic capacitances represented by capacitors Cs1 and Cs2, forexample, are included between the first coupling element 31 and thesecond coupling element 32 of the coupling circuit 30. In addition, thecoupling circuit 30 includes an inductor L3 connected between the firstcoupling element 31 and the second coupling element 32.

The inductor L3 and the capacitors Cs1 and Cs2 of parasitic capacitancesresonate in parallel. Accordingly, a reactance component generated inthe coupling circuit 30 is reduced or prevented in the parallel resonantfrequency band. Thus, a reactance component that is added by includingthe coupling circuit 30 is canceled, and a change from a matching statein which the coupling circuit 30 is not provided is able to be reducedor prevented.

Twelfth Preferred Embodiment

FIG. 28 illustrates a circuit configuration of an antenna device 112according to a twelfth preferred embodiment of the present invention.

The antenna device 112 according to the present preferred embodimentincludes the radiating element 10, the coupling circuit 30, and thenon-radiating resonant circuit 20. The feeder circuit 1 is connected tothe radiating element 10. The coupling circuit 30 includes the firstcoupling element 31 that is connected between the radiating element 10and the ground, and the second coupling element 32 coupled to the firstcoupling element 31. The non-radiating resonant circuit 20 is connectedto the second coupling element 32. Also, the inductor 35 is disposedbetween the first coupling element 31 and the ground in this example.

With the above configuration, the radiating element 10 and thenon-radiating resonant circuit 20 do not interfere with each otherregarding radiation, and a radiation characteristic of the radiatingelement 10 is not adversely affected. In addition, a frequencycharacteristic of a return loss of the radiating element 10 seen fromthe feeder circuit 1 is adjusted by a resonance characteristic of thenon-radiating resonant circuit 20, and a pole is generated in a desiredfrequency band to broaden the band of the frequency characteristic ofthe antenna. Since a current intensity is particularly high in a portionthat is connected to the ground, the radiating element 10 and thenon-radiating resonant circuit 20 are able to be coupled to each othervia the coupling circuit 30. In addition, the coupling circuit 30 andthe non-radiating resonant circuit 20 are able to be arranged with ahigher degree of freedom.

Thirteenth Preferred Embodiment

FIG. 29 illustrates a circuit configuration of an antenna device 113according to a thirteenth preferred embodiment of the present invention.

The antenna device 113 according to the present preferred embodimentincludes a substrate 5 on which the coupling circuit 30 and thenon-radiating resonant circuit 20 are each provided using conductorpatterns. The remaining configuration is the same as or similar to thatof the circuit illustrated in FIG. 4 in the first preferred embodiment.

The substrate 5 is preferably made of, for example, a resin multi-layersubstrate or a ceramic multi-layer substrate. In a case of a resinmulti-layer substrate, for example, a plurality of thermoplastic resinmaterials on surfaces of which copper-foil patterns are provided arestacked and pressed with heat. In a case of a ceramic multi-layersubstrate, a plurality of ceramic green sheets on surfaces of whichconductor-paste patterns are provided are stacked and fired.

Note that in a case in which the coupling circuit 30 and thenon-radiating resonant circuit 20 are provided on different substrates,the non-radiating resonant circuit 20 may be provided using the resinmulti-layer substrate or the ceramic multi-layer substrate.

According to the present preferred embodiment, since the couplingcircuit 30 and the non-radiating resonant circuit 20 are integrated witheach other, the area used is reduced.

Fourteenth Preferred Embodiment

A fourteenth preferred embodiment of the present invention willillustrate an antenna device including a PIFA (planar inverted-Fantenna) and a parasitic radiating element.

FIG. 30 illustrates a circuit configuration of an antenna device 114according to the fourteenth preferred embodiment. The antenna device 114according to the present preferred embodiment includes a feedingradiating element 10A, a feeding line 10AF, a parasitic radiatingelement 10B, and the coupling circuit 30. The feeder circuit 1 isconnected between the feeding line 10AF and the ground. Theconfiguration and advantageous effects of the coupling circuit 30 are asdescribed in the above-described preferred embodiments.

The first coupling element 31 of the coupling circuit 30 is connectedbetween a connection point Ps between the feeding radiating element 10Aand the feeding line AF and the ground. The feeding radiating element10A, the feeding line 10AF, and the first coupling element 31 define aPIFA. That is, the first coupling element 31 of the coupling circuit 30is provided at a portion of a short pin of the PIFA. The short pinconnects the connection point Ps and the ground to each other. Acapacitor or an inductor may be provided in this portion.

The parasitic radiating element 10B is preferably a monopole parasiticradiating element, for example. The second coupling element 32 of thecoupling circuit 30 is disposed in the vicinity of a ground end of theparasitic radiating element 10B.

A resonant current iA of the feeding radiating element flows between anopen end of the feeding radiating element 10A and a ground end of thefirst coupling element 31. In addition, a resonant current iB flowsbetween an open end of the parasitic radiating element 10B and a groundend of the second coupling element 32. A phase of the current iA flowingin the feeding radiating element 10A and a phase of the current iBflowing in the parasitic radiating element 10B are different from eachother.

In general, if the phase of resonance of the feeding radiating elementand the phase of resonance of the parasitic radiating element are thesame, a notch is present between the two resonant frequencies in afrequency characteristic of the antenna device. Therefore, the bandcannot be broadened even if the parasitic radiating element is provided.That is, the parasitic radiating element cannot be provided adjacent tothe feeding radiating element in order to broaden the band.

In contrast, in the present preferred embodiment, the current flowing inthe first coupling element 31 of the coupling circuit 30 and the currentflowing in the second coupling element 32 have a phase difference.Therefore, the phase of resonance of the feeding radiating element 10Aand the phase of resonance of the parasitic radiating element 10B arenot the same, and thus, a notch is not present between the two resonantfrequencies. The phase difference between the first coupling element 31and the second coupling element 32 is preferably, for example about 180°at most, and a phase difference of less than or equal to about 180° isgenerated by a parasitic component. That is, due to an effect of theparasitic capacitance between the first coupling element 31 and thesecond coupling element 32, the phase difference between the currentflowing in the first coupling element 31 and the current flowing in thesecond coupling element 32 is preferably greater than about 0° and lessthan about 180°, for example.

As illustrated in FIG. 30, since the resonant current iA flows betweenthe open end and the short position in the PIFA, the phase of currentflowing in the feeder circuit 1 and the phase of the resonant current iAare different from each other. Accordingly, if the first couplingelement 31 of the coupling circuit 30 is disposed in the feeding line10AF and the parasitic radiating element 10B is connected to the secondcoupling element 32, since there is no correlation between the phase ofthe current iB flowing in the parasitic radiating element 10B and thephase of the current iA flowing in the feeding radiating element 10A, asdescribed above, the resonance of the feeding radiating element 10A andthe resonance of the parasitic radiating element 10B may have the samephase, in which case, the above notch is present. In the presentpreferred embodiment, such a problem does not arise, and the parasiticradiating element 10B and the feeding radiating element 10A are able tobe provided adjacent to each other.

Although the present preferred embodiment is an example in which thefeeding radiating element is a PIFA, the feeding radiating element isnot limited to a PIFA and may be a typical inverse-F antenna. The sameor substantially the same advantageous effects are able to be obtained.

Fifteenth Preferred Embodiment

A fifteenth preferred embodiment of the present invention willillustrate an example of an antenna device including a plurality ofparasitic radiating elements.

FIG. 31A illustrates a circuit configuration of an antenna device 115according to the fifteenth preferred embodiment. The antenna device 115according to the present preferred embodiment includes the feedingradiating element 10A, the feeding line 10AF, the parasitic radiatingelement 10B, a parasitic radiating element 10C, and the coupling circuit30. The feeder circuit 1 is connected between the feeding line 10AF andthe ground.

The parasitic radiating element 10C is, at around a ground end thereof,mainly coupled to the feeding line 10AF of the feeding radiating element10A. The remaining configuration is the same as or similar to that ofthe antenna device 114 illustrated in FIG. 30.

FIG. 31B illustrates a frequency characteristic of a return loss of theantenna device 115 illustrated in FIG. 31A and an antenna deviceaccording to a comparative example. In FIG. 31B, a return losscharacteristic RL1 is a return loss of the antenna device 115 accordingto the present preferred embodiment, and a return loss characteristicRL2 is a return loss of the antenna device according to the comparativeexample. The antenna device according to the comparative example is anantenna device in which the coupling circuit 30 and the parasiticradiating element 10B are not included and the first coupling element 31merely defines and functions as a short pin of a PIFA. In either antennadevice, a pole is generated at a center frequency F1 of a low band. Thisis due to ¼ wavelength resonance of the feeding radiating element 10A.Another pole is generated at a frequency F2. This is due to ¾ wavelengthresonance of the feeding radiating element 10A. A still another pole isgenerated at a frequency F3. This is due to ¼ wavelength resonance ofthe monopole parasitic radiating element 10C.

In the antenna device 115 according to the present preferred embodiment,a pole is also generated at a frequency F0. This is due to a resonancecharacteristic of the parasitic radiating element 10B. In this manner,it is possible to provide an antenna device including the parasiticradiating element 10B that is connected to the coupling circuit 30 andthe parasitic radiating element 10C that does not interpose coupling ofthe coupling circuit 30.

Also in the present preferred embodiment, the feeding radiating elementis not limited to a PIFA and may be a typical inverse-F antenna. Thesame or substantially the same advantageous effects are obtained.

Sixteenth Preferred Embodiment

A sixteenth preferred embodiment of the present invention willillustrate an example of an antenna device including a plurality ofparasitic radiating elements.

FIG. 32 illustrates a circuit configuration of an antenna device 116according to the sixteenth preferred embodiment. The antenna device 116according to the present preferred embodiment includes the feedingradiating element 10A, the feeding line 10AF, a short pin 10AS, theparasitic radiating elements 10B and 10C, and the coupling circuit 30.The feeding radiating element 10A is a radiating element of a PIFA.

In the present preferred embodiment, the first coupling element 31 ofthe coupling circuit 30 is disposed around the ground end of theparasitic radiating element 10B, and the second coupling element 32 ofthe coupling circuit 30 is disposed around the ground end of theparasitic radiating element 10C. The parasitic radiating element 10B is,at around the ground end thereof, mainly coupled to the feeding line10AF of the feeding radiating element 10A.

As in the present preferred embodiment, the two parasitic radiatingelements 10B and 10C may be configured to be coupled to each other viathe coupling circuit 30.

Note that in the present preferred embodiment, the feeding radiatingelement is not limited to a PIFA or an inverted-F antenna, and may be,for example, a monopole radiating element. That is, any feedingradiating element that is coupled to the parasitic radiating element 10Bmay be used, and the same or substantially the same advantageous effectsare obtained.

Seventeenth Preferred Embodiment

FIG. 33 illustrates a circuit configuration of an antenna device 117according to a seventeenth preferred embodiment of the presentinvention. The antenna device 117 according to the present preferredembodiment includes feeding radiating elements 10U and 10V, the feedingline 10AF, the parasitic radiating element 10B, the parasitic radiatingelement 10C, and the coupling circuit 30. The feeder circuit 1 isconnected between the feeding line 10AF and the ground. Theconfiguration and advantageous effects of the coupling circuit 30 are asdescribed in the above preferred embodiments.

The feeding radiating elements 10U and 10V and the feeding line 10AFdefine a branch-feeding monopole antenna or a branch-feeding PIFA. Theparasitic radiating element 10C is mainly coupled with the feeding line10AF to define and function as a monopole or an inverted-L antenna.

FIG. 34 illustrates a frequency characteristic of a return loss of theantenna device 117. In FIG. 34, a pole indicated by a frequency F1 ismainly due to a fundamental wave generated in the feeding radiatingelement 10U and the feeding line 10AF in a branch antenna defined by thefeeding radiating elements 10U and 10V and the feeding line 10AF. A poleindicated by a frequency F2 is due to a fundamental wave generated inthe parasitic radiating element 10C. A pole indicated by a frequency F3is mainly caused by, for example, a ¾ wavelength harmonic generated inthe feeding radiating element 10U and the feeding line 10AF. A poleindicated by a frequency F4 is due to a fundamental wave generated inthe parasitic radiating element 10B. A pole indicated by a frequency F5is mainly due to resonance generated in the feeding radiating element10V in the branch antenna defined by the feeding radiating elements 10Uand 10V and the feeding line 10AF.

Note that a parasitic capacitance is actively generated between thefeeding radiating element 10V and the parasitic radiating element 10B sothat a phase difference of the resonant current between the feedingradiating element 10V and the parasitic radiating element 10B is about90°. Thus, a pole of the feeding radiating element 10V indicated by thefrequency F4 and a pole of the parasitic radiating element 10B indicatedby the frequency F5 are generated.

In the antenna device according to the present preferred embodiment, byincluding the branch antenna including the feeding radiating element10V, a communication band that is broadened to about 2700 MHz, forexample, is able to be covered, and a broad-band antenna that covers alow band of about 700 MHz to about 900 MHz and a high band of about 1700MHz to about 2700 MHz, for example, is able to be provided.

Eighteenth Preferred Embodiment

FIG. 35 is a circuit diagram of an antenna device 118A according to aneighteenth preferred embodiment of the present invention. In the antennadevice 118A, the parasitic radiating element 10B is provided at a sidesurface portion of the metal housing. The second coupling element 32 ofthe coupling circuit is connected to the parasitic radiating element10B. The remaining configuration is the same as or similar to that ofthe circuit illustrated in FIG. 4 in the first preferred embodiment.

With the structure of the antenna device 118A, the parasitic radiatingelement 10B is separated from the radiating element 10, and a goodradiation characteristic is able to be obtained at a resonant frequencythat is added by the coupling circuit 30 and the parasitic radiatingelement 10B. Furthermore, the radiation characteristic of the radiatingelement 10 is not degraded at frequencies other than the resonantfrequency.

FIG. 36 is a circuit diagram of another antenna device 118B according tothe eighteenth preferred embodiment. In the antenna device 118B, theparasitic radiating element 10B is provided at a side surface portion ofthe metal housing. An end portion of the parasitic radiating element 10Bis connected to the ground (is grounded) of a circuit substrate, forexample, via the inductor 8. The parasitic radiating element 10B definesand functions as a ½ wavelength resonant antenna.

With the structure of the antenna device 118B, since the tip of the sidesurface portion of the metal housing is grounded, variations in antennacharacteristic due to a change of surrounding environment is able to bereduced or prevented. Even in a case in which a side surface portion ofanother metal housing that is grounded via a slit is present forward ofthe tip of the side surface portion of the metal housing, since the tipof the side surface portion of the metal housing is grounded, a fieldmaximum point moves from the tip of the parasitic radiating element 10Btoward a center, and a good radiation characteristic is able to beobtained at a resonant frequency that is added by the coupling circuit30. Furthermore, the resonant frequency is able to be easily adjusted bythe inductance of the inductor 8.

FIG. 37 is a circuit diagram of another antenna device 118C according tothe eighteenth preferred embodiment. In the antenna device 118C, thefeeding radiating element 10A extends from an end surface portion of themetal housing to a side surface portion thereof. Similarly, theparasitic radiating element 10B is extends from an end surface portionof the metal housing to a side surface portion thereof. In this manner,the main portion of the parasitic radiating element 10B is provided atthe end surface portion of the metal housing. In addition, the parasiticradiating element 10B may be close to a ground end of the feedingradiating element 10A. With this structure, since a field maximum pointof the feeding radiating element 10A moves from the ground end toward acenter, unnecessary interference between the feeding radiating element10A and the parasitic radiating element 10B is able to be reduced orprevented.

Nineteenth Preferred Embodiment

FIG. 38 is a plan view of a main portion of an antenna device 119according to a nineteenth preferred embodiment of the present invention.

A metal housing of electronic equipment includes the radiating element10, defined by an end portion of the metal housing. A connectionposition of the feeding line 9 for the radiating element 10 and aposition of the non-radiating resonant circuit 20 differ from those inthe antenna device 101 illustrated in FIG. 2 in the first preferredembodiment.

In the present preferred embodiment, in a plan view of the circuitsubstrate 6, the feeding line 9 is connected to the left side surfaceportion 13 of the radiating element 10.

Accordingly, the non-radiating resonant circuit 20 is disposed on theright side of the coupling circuit 30. This positional relationship isan alternative configuration (symmetric relationship) to the exampleillustrated in FIG. 2. The remaining configuration is the same as orsimilar to that illustrated in the first preferred embodiment.

FIG. 39 is a perspective view of the coupling circuit 30 according tothe present preferred embodiment. The external configuration of thecoupling circuit 30 is represented by a two-dotted-and-dashed line. Onan outer surface of the coupling circuit 30, the feeder circuitconnection terminal PF, the radiating element connection terminal PA,the ground terminal PG, and the non-radiating resonant circuitconnection terminal PS are formed. The coupling circuit 30 is the sameor substantially the same as the coupling circuit 30 illustrated in FIG.1 in the first preferred embodiment. However, the second surface MS2 isthe mount surface that faces the circuit substrate. On a top surface(first surface) that is opposed to the mount surface (second surface)MS2, the direction discrimination mark DDM is provided. Thus, theposition of the terminals differ from that in the coupling circuit 30illustrated in FIG. 1 in a plan view. In the coupling circuit 30illustrated in FIG. 1, in a plan view, the ground terminal PG, thefeeder circuit connection terminal PF, and the non-radiating resonantcircuit connection terminal PS are disposed clockwise in this order fromthe radiating element connection terminal PA. In the nineteenthpreferred embodiment, as illustrated in FIG. 39, the ground terminal PG,the feeder circuit connection terminal PF, and the non-radiatingresonant circuit connection terminal PS are disposed counterclockwise inthis order from the radiating element connection terminal PA.

As described above, since the first end and the second end of the firstcoupling element and the first end and the second end of the secondcoupling element are provided on both the first surface MS1 and thesecond surface MS2, either the first surface or the second surface maydefine and function as the mount surface. Accordingly, either the firstsurface MS1 or the second surface MS2 of the coupling circuit 30 may beselected as the mount surface to be mounted on a circuit substrate suchthat the terminals are disposed at positions appropriate for theposition of a circuit or an element to which the first coupling elementand the second coupling element provided on the coupling circuit 30 areconnected.

The examples illustrated in FIG. 8 and FIG. 39 illustrate examples inwhich interlayer connection conductors that connect the four terminalsprovided on the first surface MS1 and the four terminals provided on thesecond surface MS2 to each other are provided on end surfaces of themulti-layer body. However, a plurality of via conductors may be providedinside the multi-layer body, and the four terminals provided on thefirst surface MS1 and the four terminals provided on the second surfaceMS2 may be connected to each other via these via conductors.

In addition to formation of the above via conductors, LGA (Land GridArray) terminals, for example, may preferably be provided on the mountsurface of the coupling circuit 30.

FIG. 40 illustrates a configuration of another coupling circuit 30according to the present preferred embodiment and is an exploded planview illustrating conductor patterns provided on layers of the couplingcircuit 30.

As illustrated in FIG. 40, the first conductor pattern L11, the secondconductor pattern L12, the third conductor pattern L21, and the fourthconductor pattern L22 are respectively provided on the insulatingmaterial S11, the insulating material S12, the insulating material S21,and the insulating material S22. The insulating materials S11, S12, S21,and S22 are stacked such that these coil conductor patterns are disposedin the following order from a layer close to the mount surface: thefirst conductor pattern L11, the second conductor pattern L12, the thirdconductor pattern L21, and the fourth conductor pattern L22.

A first end of the first conductor pattern L11 is connected to theradiating element connection terminal PA, and a second end thereof isconnected to a first end of the second conductor pattern L12 via theinterlayer connection conductor V1. A second end of the second conductorpattern L12 is connected to the feeder circuit connection terminal PF. Afirst end of the third conductor pattern L21 is connected to thenon-radiating resonant circuit connection terminal PS, and a second endof the third conductor pattern L21 is connected to a first end of thefourth conductor pattern L22 via the interlayer connection conductor V2.A second end of the fourth conductor pattern L22 is connected to theground terminal PG.

The conductor patterns on the layers illustrated in FIG. 40 arepreferably in a symmetric or substantially symmetrical relationship withthe conductor patterns illustrated in FIG. 9. Thus, in the couplingcircuit including these conductor patterns, in a plan view, the groundterminal PG, the feeder circuit connection terminal PF, and thenon-radiating resonant circuit connection terminal PS are disposedcounterclockwise in this order from the radiating element connectionterminal PA.

As in this example, the terminals may be disposed at positionsappropriate for the position of a circuit or an element to which thefirst coupling element and the second coupling element provided in thecoupling circuit 30 are connected.

Twentieth Preferred Embodiment

A twentieth preferred embodiment of the present invention willillustrate an antenna device further including a phase shifter.

FIG. 41 is a circuit diagram of an antenna device 120 according to thetwentieth preferred embodiment in which the feeder circuit 1 isconnected. In the antenna device 120, a phase shifter 50 is connectedbetween the feeder circuit 1 and the first coupling element 31 of thecoupling circuit 30. The phase shifter 50 is a phase shifter by which aphase shift amount changes depending on the frequency (has frequencydependency). The phase shifter 50 includes a first coil Lp, a secondcoil Ls, and a capacitor C3 that are coupled to one another.

Note that in this example, capacitors C4 and C5 that provide impedancematching are connected between the feeder circuit 1 and the phaseshifter 50.

The configuration of the coupling circuit 30, the radiating element 10,and the non-radiating resonant circuit 20 is the same as or similar tothat illustrated in the first preferred embodiment.

FIG. 42 is an equivalent circuit diagram illustrating the phase shifter50 in which an ideal transformer IT and parasitic inductance components(series parasitic inductance components La and Lc and parallel parasiticinductance component Lb) are separately illustrated.

The coupling coefficient between the first coil Lp and the second coilLs illustrated in FIG. 41 is lower than that of a common high-frequencytransformer, and accordingly, the series parasitic inductance componentLc is large. However, since the capacitance of the capacitor C3 is alsolarge, impedance matching is ensured. In addition, since the capacitanceof the capacitor C3 is large, a ratio of a high-band signal bypassingthe capacitor C3 is higher than that bypassing the transformer definedby the first coil Lp and the second coil Ls, and a phase shifting effectof the transformer is small. On the other hand, for a low band, theamount bypassing the capacitor C3 is relatively small, and the phaseshifting effect of the transformer is large. Thus, the couplingcoefficient is preferably determined such that the phase shift amountwith respect to a low-band signal is about 180° and the phase shiftamount with respect to a high-band signal is about 90°, for example.

FIG. 43 illustrates a frequency characteristic of the phase shift amountof the phase shifter 50. In this example, for example, the phase shiftamount in a low band (about 700 MHz to about 900 MHz band, for example)is preferably about 180°, and the phase shift amount in a high band(about 1.7 GHz to about 2.7 GHz band, for example) is preferably about90°.

Next, effects obtained by providing the phase shifter 50 together withthe coupling circuit 30 will be described. FIG. 44A is a circuit diagramof the antenna device illustrated in the first preferred embodiment,which does not include the phase shifter 50, and FIG. 44B illustratesimpedance loci representing, on a Smith chart, impedances when seeingthe antenna device from the feeder circuit 1.

FIG. 45A is a circuit diagram of an antenna device to which the phaseshifter 50 is included, and FIG. 45B illustrates impedance locirepresenting, on a Smith chart, impedances when seeing the antennadevice from the feeder circuit 1. This antenna device is a circuit thatdoes not include the capacitor C5 in the circuit illustrated in FIG. 41.

FIG. 46A is a circuit diagram of an antenna device including theimpedance matching capacitor C5 (the same as or similar to thatillustrated in FIG. 41), and FIG. 46B illustrates an impedance locusrepresenting, on a Smith chart, an impedance when seeing the antennadevice from the feeder circuit 1.

In FIG. 44B, locus T0 is an impedance locus of an antenna deviceaccording to a comparative example in which the coupling circuit 30 andthe non-radiating resonant circuit 20 are not provided, and locus T1 isan impedance locus of the antenna device illustrated in FIG. 44A. Bothare results obtained by a sweep from about 1.7 GHz to about 2.7 GHz. Asis clear from FIG. 44B, by including the coupling circuit 30 and thenon-radiating resonant circuit 20, as described above, a pole (smallloop on chart) is generated in the frequency characteristic of theantenna, and accordingly, the resonant frequency band moves toward thecenter of the chart. Note that a higher frequency band is present in aperiphery of the chart, and it is discovered that matching is difficultin the high frequency band.

In FIG. 45B, locus T2 is an impedance locus of the antenna deviceincluding the phase shifter 50, the coupling circuit 30, and thenon-radiating resonant circuit 20, and locus T1 is the same as orsimilar to locus T1 illustrated in FIG. 44A. Both are results obtainedby a sweep from about 1.7 GHz to about 2.7 GHz. As is clear from FIG.45B, by including the phase shifter 50, the phase advances by about 180°in a low band, and the phase advances by about 90° in a high band.Accordingly, the high-frequency band also moves toward the center of thechart.

In FIG. 46B, locus T3 is an impedance locus of the antenna deviceillustrated in FIG. 46A, and is a result obtained by a sweep from about1.7 GHz to about 2.7 GHz. As is clear from comparison with locus T2illustrated in FIG. 45B, by a function of the capacitor C5 that isshunt-connected, the high-frequency band rotates clockwise. Thus,matching is improved in all frequency bands.

FIG. 47 illustrates a frequency characteristic of a return loss of theantenna devices illustrated in FIG. 44A and FIG. 46A and the antennadevice according to the comparative example. In FIG. 47, a return losscharacteristic RL1 is a return loss characteristic of the antenna deviceaccording to the comparative example, in which the coupling circuit 30and the non-radiating resonant circuit 20 are not included, a returnloss characteristic RL2 is a return loss characteristic of the antennadevice illustrated in FIG. 44A, and a return loss characteristic RL3 isa return loss characteristic of the antenna device illustrated in FIG.46A. The return loss characteristics RL1 and RL2 in FIG. 47 are the sameas those illustrated in FIG. 6. Comparing the return losscharacteristics RL2 and RL3 with each other, it is discovered that thereturn loss is small in all bands and that the high band is broadened toa wide band of, for example, from about 1.4 GHz to about 2.6 GHz, whileusing the same radiating element.

FIG. 48 is an external perspective view of the phase shifter 50, andFIG. 49 is a plan view of layers in the phase shifter 50. In addition,FIG. 50 is a sectional view of the phase shifter 50.

A top surface of a material S1 corresponds to a mount surface (bottomsurface) of a multi-layer body 100. On the material S1, a terminal T1 asa first port P1, a terminal T2 as a second port P2, a ground terminal G,and an open terminal NC are provided.

The material layers of the multi-layer body 100 may preferably be, forexample, a non-magnetic ceramic multi-layer body made of LTCC or othersuitable material or a resin multi-layer body made of a resin material,such as polyimide or liquid crystal polymer. In this manner, since thematerial layers are non-magnetic (not a magnetic ferrite), it ispossible to use the material layers as a transformer and a phase shifterwith a predetermined inductance and a predetermined coupling coefficienteven in a high frequency band exceeding several hundreds of MHz.

Each of the conductor patterns and the interlayer connection conductorsis preferably made of, for example, a conductor material including Ag orCu as a main component and having a small resistivity. In a case inwhich the material layers are ceramic, for example, the conductorpatterns and the interlayer connection conductors are preferably formedby screen printing and firing of a conductive paste including Ag or Cuas a main component. In a case in which the material layers are resin,for example, the conductor patterns and the interlayer connectionconductors are preferably patterned by etching or other suitable methodof a metal foil such as an Al foil or a Cu foil.

The phase shifter 50 includes a plurality of insulating materials S1 toS9. Various conductor patterns are provided on the materials S1 to S9.The “various conductor patterns” include not only conductor patternsprovided on surfaces of the materials but also interlayer connectionconductors. The interlayer connection conductors include not only viaconductors but also end surface electrodes provided on end surfaces ofthe multi-layer body.

The top surface of the material S1 corresponds to the mount surface(bottom surface) of the multi-layer body. On the material S1, theterminal T1 as the first port P1, the terminal T2 as the second port P2,the ground terminal G, and the open terminal NC are provided.

On the materials S5 and S4, conductors L1A1 and L1A2 are provided,respectively. On the material S3, conductors L1A3 and L1B1 are formed.On the material S2, conductors L1B2 and L1C are provided.

A first end of the conductor L1A1 is connected to the terminal T1 as thefirst port. A second end of the conductor L1A1 is connected to a firstend of the conductor L1A2 via an interlayer connection conductor V11. Asecond end of the conductor L1A2 is connected to a first end of theconductor L1A3 via an interlayer connection conductor V12. A second endof the conductor L1A3 is connected to a first end of the conductor L1B1.The second end of the conductor L1A3 and the first end of the conductorL1B1 are connected to a first end of the conductor L1B2 via aninterlayer connection conductor V13. A second end of the conductor L1B1is connected to a second end of the conductor L1B2 via an interlayerconnection conductor V14. The second end of the conductor L1B2 isconnected to a first end of the conductor L1C. A second end of theconductor L1C is connected to the ground terminal G.

On the materials S6 and S7, conductors L2A1 and L2A2 are provided,respectively. On the material S8, conductors L2A3 and L2B1 are formed.On the material S9, conductors L2B2 and L2C are provided.

A first end of the conductor L2A1 is connected to the terminal T2 as thesecond port. A second end of the conductor L2A1 is connected to a firstend of the conductor L2A2 via an interlayer connection conductor V21. Asecond end of the conductor L2A2 is connected to a first end of theconductor L2A3 via an interlayer connection conductor V22. A second endof the conductor L2A3 is connected to a first end of the conductor L2B1.The second end of the conductor L2A3 and the first end of the conductorL2B1 are connected to a first end of the conductor L2B2 via aninterlayer connection conductor V23. A second end of the conductor L2B1is connected to a second end of the conductor L2B2 via an interlayerconnection conductor V24. The second end of the conductor L2B2 isconnected to a first end of the conductor L2C. A second end of theconductor L2C is connected to the ground terminal G.

The conductors L1A1, L1A2, L1A3, L1B1, L1B2, and L1C and the interlayerconnection conductors V11, V12, V13, and V14 define the first coil Lp.In addition, the conductors L2A1, L2A2, L2A3, L2B1, L2B2, and L2C andthe interlayer connection conductors V21, V22, V23, and V24 define thesecond coil Ls. Both of the first coil Lp and the second coil Ls arepreferably rectangular or substantially rectangular helical coils, forexample.

Twenty-First Preferred Embodiment

A twenty-first preferred embodiment of the present invention willillustrate a radiating element having a structure that is different fromthat of the radiating element illustrated in the first preferredembodiment.

FIG. 51 is a plan view of a portion of a metal housing of electronicequipment. The metal housing of electronic equipment includes theradiating element 10, which is defined by an end portion of the metalhosing, and the metal housing main portion 40. Although the firstpreferred embodiment illustrated an example in which the end portion ofthe metal housing including three sides in a plan view is used as theradiating element 10, as illustrated in FIG. 51, the radiating element10 may be defined by a planar end portion of the metal housing.

FIGS. 52A and 52B are perspective views of portions of metal housings ofdifferent pieces of electronic equipment. In an example illustrated inFIG. 52A, the radiating element 10, which is defined by the end portionof the metal housing, includes a plane parallel or substantiallyparallel to the X-Y plane and a plane parallel or substantially parallelto the Y-Z plane. In an example illustrated in FIG. 52B, the radiatingelement 10, which is defined by the end portion of the metal housing,includes a plane parallel or substantially parallel to the X-Y plane, aplane parallel or substantially parallel to the Y-Z plane, and twoplanes parallel or substantially parallel to the X-Z plane.

As illustrated in FIGS. 52A and 52B, the end portion of the metalhousing may have various shapes.

The above-described preferred embodiments have illustrated examples inwhich the end portion of the metal housing is used as the radiatingelement. However, a portion of the radiating element or the entireradiating element may be a conductor pattern provided on a circuitsubstrate, for example, or may be a member different from the housing.

Although the example illustrated in FIG. 4 illustrates a case in which aparasitic capacitance is generated between an end of the radiatingelement 10 and the ground, a capacitance having a low impedance in ahigh band may be actively provided at this position so as to cause theradiating element 10 to define and function as a PIFA. In addition, theposition at which the capacitance is generated may be connected to theground to define and function as a PIFA.

The linear conductor pattern of the non-radiating resonant circuit 20 isnot limited to a shape that returns and may extend in one direction.Alternatively, the non-radiating resonant circuit 20 may be bent in anL-shape or may be curved, for example. Furthermore, the non-radiatingresonant circuit 20 may include a conductor pattern that splits into aplurality of branches. Thus, a plurality of poles are able to begenerated.

In addition, the non-radiating resonant circuit 20 may include a tip ofthe linear conductor pattern connected to the ground so as to define andfunction as a circuit similar to a short stub.

In the above-described examples, examples of using fundamental waveresonance of the non-radiating resonant circuit 20 have mainlydescribed. However, any harmonic resonance of the non-radiating resonantcircuit 20, such as double-wave resonance (secondary resonance),triple-wave resonance (tertiary resonance), or 3/2-wave resonance, forexample, may also be used. In addition, both of the fundamental waveresonance and the harmonic resonance may be used, or a plurality ofharmonic resonances may be used.

As for the radiating element 10, similarly, any harmonic resonance, suchas double-wave resonance (secondary resonance), triple-wave resonance(tertiary resonance), or 3/2-wave resonance, for example, may also beused. In addition, both of the fundamental wave resonance and theharmonic resonance may be used, or a plurality of harmonic resonancesmay be used.

The above-described preferred embodiments have illustrated a smartphoneor electronic equipment having the same shape as the smartphone.However, the preferred embodiments may be similarly applied to varioustypes of electronic equipment, such as a mobile phone including afeature phone, a wearable terminal including a smart watch and smartglasses, a lap top PC, a tablet terminal, a camera, a game console, atoy, or other suitable devices, for example.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

What is claimed is:
 1. An antenna device comprising: a radiatingelement; a coupling circuit including a first coupling element and asecond coupling element, the first coupling element being connectedbetween the radiating element and a feeder circuit, the second couplingelement being coupled to the first coupling element; and a non-radiatingresonant circuit connected to the second coupling element; wherein thenon-radiating resonant circuit is fed by the feeder circuit through thecoupling circuit; and a frequency characteristic of a return loss of theradiating element is adjusted by a resonant frequency characteristic ofthe non-radiating resonant circuit.
 2. The antenna device according toclaim 1, further comprising: a ground; wherein a direction of a magneticfield generated when current flows in the first coupling element in adirection from a terminal connected to the feeder circuit to a terminalconnected to the radiating element is opposite to a direction of amagnetic field generated when current flows in the second couplingelement in a direction from a terminal connected to the non-radiatingresonant circuit to a terminal connected to the ground.
 3. The antennadevice according to claim 1, wherein the first coupling element and thesecond coupling element are multi-layered coil conductor patterns, andthe coupling circuit defines a transformer in which the first couplingelement and the second coupling element are electromagnetically coupledto each other.
 4. The antenna device according to claim 1, wherein atleast half of the non-radiating resonant circuit is included within aformation region of the radiating element in a plan view of theradiating element.
 5. The antenna device according to claim 1, whereinthe radiating element is defined by a conductive member that includesthree sides in a plan view, and the non-radiating resonant circuit issurrounded by the three sides in a plan view.
 6. The antenna deviceaccording to claim 1, wherein the non-radiating resonant circuit isdefined by a linear conductor pattern that includes a returning portionalong the linear conductor.
 7. The antenna device according to claim 6,wherein the conductor pattern includes a first linear conductor patternportion that extends from the coupling circuit and a second conductorpattern portion that returns, at the returning portion, to be spacedaway from the radiating element.
 8. The antenna device according toclaim 1, further comprising a phase shifter that is connected betweenthe feeder circuit and the first coupling element and that has afrequency dependency.
 9. The antenna device according to claim 1,further comprising: a ground; wherein a second terminal of the secondcoupling element is connected to the ground, the second terminal beingopposite to a first terminal to which the non-radiating resonant circuitis connected; and a length of a line between the first coupling elementand the feeder circuit and a length of a line between the secondterminal of the second coupling element and the ground are each lessthan about ⅛ wavelength of a resonant frequency.
 10. The antenna deviceaccording to claim 9, further comprising an inductor that is connectedbetween the first terminal of the second coupling element and theground.
 11. The antenna device according to claim 9, further comprisinga capacitor that is connected between the first terminal of the secondcoupling element and the ground.
 12. The antenna device according toclaim 1, further comprising an inductor that is connected between thesecond coupling element and the non-radiating resonant circuit.
 13. Theantenna device according to claim 1, further comprising a capacitor thatis connected between the second coupling element and the non-radiatingresonant circuit.
 14. The antenna device according to claim 1, furthercomprising: a second coupling circuit including a third coupling elementand a fourth coupling element, the third coupling element beingconnected between the first coupling element and the feeder circuit, thefourth coupling element being coupled to the third coupling element; anda second non-radiating resonant circuit connected to the fourth couplingelement.
 15. The antenna device according to claim 1, furthercomprising: a second coupling circuit including a third coupling elementand a fourth coupling element, the third coupling element beingconnected between the second coupling element and the non-radiatingresonant circuit, the fourth coupling element being coupled to the thirdcoupling element; and a second non-radiating resonant circuit connectedto the fourth coupling element.
 16. The antenna device according toclaim 1, further comprising: a ground; and a switch connected betweenthe non-radiating resonant circuit and the ground.
 17. The antennadevice according to claim 1, wherein the coupling circuit includes aparasitic capacitance; and the antenna device further includes aninductor that is connected to the coupling circuit and that reduces orprevents a reactance component generated in the coupling circuit byparallel resonance with the parasitic capacitance.
 18. Electronicequipment comprising: the antenna device according to claim 1; and ahousing in which the feeder circuit is accommodated; wherein a portionof the radiating element or an entirety of the radiating element isdefined by a portion of the housing.
 19. The electronic equipmentaccording to claim 18, further comprising: a ground; wherein a directionof a magnetic field generated when current flows in the first couplingelement in a direction from a terminal connected to the feeder circuitto a terminal connected to the radiating element is opposite to adirection of a magnetic field generated when current flows in the secondcoupling element in a direction from a terminal connected to thenon-radiating resonant circuit to a terminal connected to the ground.20. An antenna device comprising: a radiating element to which a feedercircuit is connected; a coupling circuit including a first couplingelement and a second coupling element, the first coupling element beingconnected between the radiating element and a ground, the secondcoupling element being coupled to the first coupling element; and anon-radiating resonant circuit connected to the second coupling element;wherein the non-radiating resonant circuit is fed by the feeder circuitthrough the coupling circuit; and a frequency characteristic of a returnloss of the radiating element is adjusted by a resonant frequencycharacteristic of the non-radiating resonant circuit.